docs: def _get_daily_data_collections(self, data_type, unit, values):
          """Return an empty data collection."""
          data_header = Header(data_type=data_type, unit=unit,
                               analysis_period=self.analysis_period,
                               metadata={'source': self._location.source,
                                         'country': self._location.country,
                                         'city': self._location.city})
          return HourlyContinuousCollection(data_header, values)